1. Field of the Invention
This invention relates to a method for reforming low grade coal to a carbonaceous material suitable for the production of metallurgical coke.
2. Brief Description of the Prior Art
Whilst improvements in the properties of coke, and particularly of metallurgical coke, have been desired because of the increasing scale of blast furnaces, heavy coking coal required for the production of good quality coke is available only in a limited number of countries, and it has now become increasingly difficult to secure a supply of such coal, both in terms of quantity and price. It appears that this trend will continue even with an increasing momentum, and it has been considered to be essential that a commercial process be developed for the production of metallurgical coke mainly from low grade coals such as steam coal (noncoking coal) and soft coking coal. Some techniques such as the briquette-blend coke production method, the preheated coal charging process and the formed coke production process have been developed and, though on a limited scale, have been put to commercial use.
Nonetheless, these known processes require a certain redesign of the coke oven, and it is difficult to produce coke using the existing equipment from a charge composed predominantly of low grade coals with any significant reduction in the blending ratio of heavy coking coal to the total charge of coal mixture.
Regarding the techniques hitherto known for reforming coal, the hydrotreating method has been available in many versions. However, these prior art processes generally consist of the steps of mixing a powdered coal with a hydrocarbon or other solvent and, if desired, further with a catalyst such as an iron-sulfur type or iron compound-sulfur type catalyst to prepare a slurry, passing the slurry through a pre-heater, adding a reducing gas, if desired, either before or after (preferably before) the preheating step, causing the preheated slurry to react with the reducing gas in a reactor at elevated temperature and pressure and separating the resultant reaction mixture into its gaseous, liquid and solid fractions. However, these methods are primarily intended to extract sulfur from coal, or to produce heavy oil. Because the quality of the product is considerably influenced by such factors as the degree of hydrogenation, reaction temperature and pressure, conditions under which the product is isolated, catalyst used, etc., they cannot be readily adapted to the reforming of low grade coals for the production of metallurgical coke.